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EP-2017-028

(Submitted on 21 Feb 2017)

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Abstract

Asymmetries in the time-dependent rates of $D^0 \to K^+K^-$ and $D^0 \to
\pi^+\pi^-$ decays are measured in a $pp$ collision data sample collected with
the LHCb detector during LHC Run 1, corresponding to an integrated luminosity
of $3\,\mathrm{fb}^{-1}$. The asymmetries in effective decay widths between
$D^0$ and $\overline{D}^0$ decays, sensitive to indirect $CP$ violation, are
measured to be $A_\Gamma(K^+ K^-) = (-0.30 \pm 0.32 \pm 0.10)\times 10^{-3}$
and $A_\Gamma(\pi^+\pi^-) = (0.46 \pm 0.58 \pm 0.12)\times 10^{-3}$, where the
first uncertainty is statistical and the second systematic. These measurements
show no evidence for $C\!P$ violation and improve on the precision of the
previous best measurements by nearly a factor of two.

Distribution of $\ln(\chi^2_{\text{IP}} ( D ^0 ))$ for the $ D ^0 \!\rightarrow K ^+ K ^- $
candidates selected in the second of the three 2012 data taking periods with magnetic field pointing downwards.
The unbinned maximum likelihood fit results are overlaid. Gaussian kernels are used to smooth the combinatorial and partially reconstructed backgrounds.

This ZIP file contains supplementary material for the publication
LHCb-PAPER-2016-063. The files are:
supplementary.pdf : An overview of the extra figures
*.pdf, *.png, *.eps : The figures in various formats